1. Field of the Invention
The present invention relates in general to an antenna and, in particular, to a planar antenna. More particularly, the present invention relates to a coupled dual-band dipole antenna having an interference-cancellation gap for wireless applications such as Wi-Fi™, wireless HDTV, Bluetooth, Public Safety, RFID, WIMAX, tolling, remote control and unlicensed band wireless applications. The invention is suitable for use in any wireless application, including, but not limited to those which use 2400-2500 MHz and 4900-6000 MHz bands.
2. Background of the Invention
In recent years there has been a tremendous increase in the use of wireless devices. The increased use has filled all or nearly all existing frequency bands. As a result, new wireless frequency standards continue to emerge throughout the world.
Based on the IEEE 802.11 standards, Wi-Fi™ has become the de facto standard for wireless local area network (WLAN) devices, which includes cell phones, smart phones and PDA devices, and laptop and desktop personal computers. Extensive efforts have been devoted to the development of an antenna that can be used to cover the entire frequency range of the latest Wi-Fi™ standard to keep overall device costs down by not requiring two separate antennas for each band while still maintaining optimal efficiency and gain in both bands.
For the latest dual-band Wi-Fi antennas, increased interference is problematic in the 2.4 and 5 GHz frequency modes. It has also been difficult for a single antenna to be optimized for both frequency modes. Currently antennas are either optimized for one frequency or another or performance in both modes results in poor efficiency. Previously disclosed planar antennas include, for example, those disclosed in U.S. Pat. No. 6,917,339 B2 to Li et al. for Multi-Band Broadband Planar Antennas; U.S. Pat. No. 6,346,914 B1 to Annamaa for Planar Antenna Structure